Modern electronic devices and/or systems are often constructed from a number of functional blocks that are connected together. These devices have signal inputs and signal outputs as well as control inputs that specify the state of various components in the device. The number of possible signal paths and operating configurations of even relatively simple devices can present problems for a test engineer who must design a series of tests to determine if the device is functioning as designed, and if it is not so functioning, isolating the component that has failed so that the component can be replaced.
Consider a simple device that has ten stages that are connected in series with each stage having two possible functional blocks that are selected by setting a switch that is part of each stage. There are 1024 possible different signal paths through the device depending on the settings of the switches. In principle, one could run tests using each of the configurations; however, even in this simple example, the testing workload and/or time can be prohibitive, particularly if each configuration requires that some parameter in the input signal such as frequency be swept over a large number of values and the outputs for each frequency analyzed.
It would be advantageous to be able to automatically design a minimum set of test configurations that “exercise” each component in the device under test (DUT). If any of the exercise tests fail, a second set of tests would then be used to isolate the defective component. Again, it would be advantageous to provide a system that automatically designs a minimum isolation test set that allows the test engineer to isolate the problem to a single component.
It would also be advantageous to provide a system that facilitates the design of the device and tests by providing additional test points within the device that would allow for more efficient testing. The design engineer is primarily concerned with providing a device that works for its intended purpose assuming all of the functional blocks perform as designed. However, the design engineer often does not have the ability to determine the most efficient use of test points within the device. That is, given a design, are there one or more additional test points that could be incorporated in the device that would significantly reduce the size of the exercise or isolation test sets for that device?
Finally, the individuals who design a device are not necessarily the individuals who must design the test system for the device. At the end of the design process, it would be advantageous to provide a graphical description of the device that facilitates the testing of the device during test and repairs. Ideally, such a description captures the design in a manner that facilitates the documentation of the device so that test engineers and technicians can quickly understand the layout of the device and the components that are currently being tested.